Abstract
In our study, Trypsin Inhibitor (TI) was inactivated remarkably by heating with soybean llS protein (11S). Then, denaturation of TI by heating was investigated as a change of the affinity of TI for trypsin. That is, the value of TI activity which made half the affinity of trypsin for the substrate was obtained by the plot of Lineweaver-Burk (defined as Kt), and the Kt of each TI was compared. The Kt of each TI obtained by DEAE-cellulose was about 15-100unit, and these values changed little after heating at 100°C for 15min.. However, when TI was heated with llS, the value of Kt increased 1.5-5 times and the affinity of TI for trypsin declined remarkably. Since it was presumed that the Kt of TI in soybean products changed because TI in soybean products received heat treatment with llS during processing, the Kt of TI in soybean products was measured, and the TI was investigated. As a result, the Kt of TI in Tonyu was 30 units but that of TI in the other soybean products was unmeasurable, because no effects of TI on Km value was seen when TI was added up to 500 units. Following this, TI in soybean products was added to the reaction mixture of trypsin and a substrate to investigate the ability of TI to compete with the substrate for trypsin. As a result, the reaction between trypsin and the substrate immediately stopped by adding TI in Tonyu, but the other soybean products showed no effects for this reaction. The above results indicate that TI in almost all soybean products, while having remaining the anti-tryptic activity, remarkably reduced its affinity for trypsin by heating with llS and practically had no effect on trypsin activity.
